Home heating systems which utilize air from outside the home for combustion purposes offer significant advantages over conventional home heating systems, which draw combustion air from inside the home. Among these advantages are: (1) fuel savings due to the fact that heated room air is not being expelled up the chimney to be replaced by cold air seeping into the home; and (2) the elimination of the need for a humidifier to keep room air at a livable humidity level.
Because such systems draw cold air into their burner units rather than drawing air that has already been heated, the firebox temperature of such systems may be slightly lower than that of conventional systems. Additionally, as the stack gases proceed up the chimney, moisture contained in those gases condenses on the inside of the chimney, where it may cause chimney freeze up. Finally, the hot combustion gases being exhausted up the chimney represent wasted heat, which could be used for further room heating.
It is known in conventional furnace systems to utilize the hot stack gases for room heating by diverting the stack gases through a heat exchanger which distributes some of the heat from the flue gases to inside air. One such system is disclosed in U.S. Pat. No. 3,813,039. Heretofore, however, there has not been a furnace system which not only utilized the heat from flue exhaust gases to heat up air circulating within the home, but also was adapted to draw cold air from outside the home for combustion purposes, raise the temperature of that air slightly so as to increase the temperature of the firebox, and decrease the temperature and moisture content of the flue gases.
In the past, industrial combustion systems, such as coal-burning power plants, have utilized cyclone separators, electrostatic precipitators, and wet scrubbers to clean the stack gases of fly ash and pollutants. One of the problem pollutants has been sulphur, which is exhausted to atmosphere as sulphur dioxide. Power plants and commercial boilers thus utilize expensive, extremely tall chimney stacks to exhaust noxious gases well away from residential levels. Until the present invention, a system has not been known which satisfactorily scrubs the pollutants from the stack gases, eliminating the need for very high chimneys, and retrieves heat energy for subsequent work.